RE: [PATCH] Hexagon (target/hexagon) TCG generation cleanup

[Taylor Simpson]

> -Original Message-
> From: Richard Henderson 
> Sent: Monday, March 15, 2021 8:40 AM
> To: Taylor Simpson ; qemu-devel@nongnu.org
> Cc: phi...@redhat.com
> Subject: Re: [PATCH] Hexagon (target/hexagon) TCG generation cleanup
>
> On 3/14/21 10:54 PM, Taylor Simpson wrote:
> > Simplify TCG generation of hex_reg_written
> >
> > Address feedback from Richard Henderson
> <
> >
> > Signed-off-by: Taylor Simpson 
> > ---
> >   target/hexagon/genptr.c | 12 +---
> >   1 file changed, 9 insertions(+), 3 deletions(-)
> >
> > diff --git a/target/hexagon/genptr.c b/target/hexagon/genptr.c
> > index 7481f4c..0ad63fe 100644
> > --- a/target/hexagon/genptr.c
> > +++ b/target/hexagon/genptr.c
> > @@ -43,9 +43,15 @@ static inline void gen_log_predicated_reg_write(int
> rnum, TCGv val, int slot)
> >   tcg_gen_movcond_tl(TCG_COND_EQ, hex_new_value[rnum],
> slot_mask, zero,
> >  val, hex_new_value[rnum]);
> >   #if HEX_DEBUG
> > -/* Do this so HELPER(debug_commit_end) will know */
> > -tcg_gen_movcond_tl(TCG_COND_EQ, hex_reg_written[rnum],
> slot_mask, zero,
> > -   one, hex_reg_written[rnum]);
> > +/*
> > + * Do this so HELPER(debug_commit_end) will know
> > + *
> > + * Note that slot_mask indicates the value is not written
> > + * (i.e., slot was cancelled), so we negate the value before
> > + * or'ing with hex_reg_written[rnum].
> > + */
> > +tcg_gen_xori_tl(slot_mask, slot_mask, 1 << slot);
> > +tcg_gen_or_tl(hex_reg_written[rnum], hex_reg_written[rnum],
> slot_mask);
>
> reg_written appears to be a boolean, not a mask of any kind.
> I think you want
>
>  tcg_gen_setcond_i32(TCG_COND_EQ, slot_mask, slot_mask, zero);
>
> and not the xor.

I'm treating it as a zero/non-zero value.  The change works because the usage 
in op_helper.c is
if (env->reg_written[i]) ...

I'll change the xor to setcond to make it more clear.


Thanks,
Taylor

Re: [PATCH] Hexagon (target/hexagon) TCG generation cleanup

[Richard Henderson]

On 3/14/21 10:54 PM, Taylor Simpson wrote:

Simplify TCG generation of hex_reg_written

Address feedback from Richard Henderson <

Signed-off-by: Taylor Simpson 
---
  target/hexagon/genptr.c | 12 +---
  1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/target/hexagon/genptr.c b/target/hexagon/genptr.c
index 7481f4c..0ad63fe 100644
--- a/target/hexagon/genptr.c
+++ b/target/hexagon/genptr.c
@@ -43,9 +43,15 @@ static inline void gen_log_predicated_reg_write(int rnum, 
TCGv val, int slot)
  tcg_gen_movcond_tl(TCG_COND_EQ, hex_new_value[rnum], slot_mask, zero,
 val, hex_new_value[rnum]);
  #if HEX_DEBUG
-/* Do this so HELPER(debug_commit_end) will know */
-tcg_gen_movcond_tl(TCG_COND_EQ, hex_reg_written[rnum], slot_mask, zero,
-   one, hex_reg_written[rnum]);
+/*
+ * Do this so HELPER(debug_commit_end) will know
+ *
+ * Note that slot_mask indicates the value is not written
+ * (i.e., slot was cancelled), so we negate the value before
+ * or'ing with hex_reg_written[rnum].
+ */
+tcg_gen_xori_tl(slot_mask, slot_mask, 1 << slot);
+tcg_gen_or_tl(hex_reg_written[rnum], hex_reg_written[rnum], slot_mask);


reg_written appears to be a boolean, not a mask of any kind.
I think you want

tcg_gen_setcond_i32(TCG_COND_EQ, slot_mask, slot_mask, zero);

and not the xor.


r~